You should be able to buy an unlocked GSM version and use it on any GSM network stateside (At&t/T-Mobile). It’ll cost a lot more upfront.
Also, outside of the carrier branding the 900 to me is the better phone. “4G”, front facing camera and for me the screen is also more appealing to me on the 900. If you haven’t owned a phone with a 4+" screen you’ll feel like all of them are huge, but after having one (4.6") I won’t go back to something as small as the iPhone screen.